In production processes, resource utilization may be planned within a planning unit. Processes are planned to be run on resources. During execution, the processes may be executed on the resources as planned. Running a process may include various steps, such as: setup the resource, production on the resource, and possibly tear or shut down the resource.
A process may be an activity or operation on a resource. A resource may be, for example, a machine, a utility, a material, a production plant, a transportation unit, or any other means suitable for working, producing, transporting, or packing a product, material, or assembly.
If a process is executed on a machine, the duration of a production step is determined by the machine itself, i.e., the duration of the production section on the machine is related to the rate or throughput of the machine.
However, the setup time for setting up a resource often may not only be determined by the resource itself, but also by predecessor processes running on the resource and the materials used on the resource for the present process.
The scheduling of processes should take into account information about predecessor processes and materials when executing the process planning. A certain sequence of processes may be assumed and depending on this sequence, setup times for resources may be estimated. These setup times depend at least on the process itself and the predecessor process.
During execution, an execution unit can read the process plan from a database and utilize the resources according to this plan. Process progress may be reported back to the scheduling unit from the execution unit and stored in a database. This feedback, however, may influence the planning, such as when progress of a process is not in conformance with a planned progress. During production, the storage of feedback of a process progress may influence the planning of the following processes. Due to the feedback, the processes may be automatically rescheduled to be in conformance with the actual situation at the execution.
In the very short term horizon, e.g., near the time of execution, the sequence of processes should not change. Nevertheless, the real data from the execution feedback may change the planning situation when the sequence of processes is scheduled automatically. This may cause a process backlog because of late confirmations of processes. Processes may be confirmed late due to confirmations of processes being reported to scheduling late, after actual execution of the processes, or due to the sequence in which the processes are confirmed differing from the planned sequence.
The result of the interplay of process planning and process execution can be seen in the following example. After each process confirmation, the sequence dependent setup times of concerned, not confirmed processes have to be adjusted. This happens automatically, because in this example the confirmed date differs from the planned date.
Automatically rescheduling the sequence of processes may confuse the process planner. After each process confirmation, the setup times may change within the planning board, resulting in changed sequences of process.
In view of the foregoing, there is a need for systems and methods for process planning that takes into account short term planning. The process planning in short term needs to be predictable and reliable. Short term changes to the actual sequence of processes should not influence the previously planned sequence of processes.